Tag Archives: Isaac newton

Physical laws have existed since the beginning of time, but they had to be discovered for science to become relevant. Scientific knowledge was built mainly by a series of small advances and adjustments, however, a few major discoveries by a few scientists have altered the course of the scientific endeavor. The age of modern science was pioneered by men like Copernicus, Galileo and Kepler. They began to examine the patterns in nature, and discovered that in some situations the workings of nature could be explained, and even predicted. They found that nature’s harmony was governed by physical laws, which were at least partly accessible to human comprehension. They studied the motion of objects on earth, and then turned their attention to the heavens. They charted the movement of the celestial bodies in great detail, and discovered that the motion of the celestial bodies could also be predicted. The gateway to scientific discovery had been opened—the universe would soon begin to reveal its most profound secrets.

In the early years, it was Isaac Newton’s insight that stood above all others. He discovered gravity as the force responsible for the motion of the moon and the planets. And as the story goes, the same force responsible for an apple falling from a tree. In 1687, he published the Principia Mathematica, where he disclosed his law of universal gravitation and the three laws of motion. It was a major breakthrough in advancing the scientific cause. Newton’s laws provided the foundation for what has become known as classical physics. For more than 300 years his equations have stood the test of time. In fact, Newton’s equations were all that was needed to plot the course that placed men on the moon. Although his equations provided an accurate mathematical framework (actually a very close approximation that was later revised by Einstein), Newton had no idea what mechanism was responsible for the effects of gravity. It is also believed that he regarded space, the arena of motion, to be absolute and unchangeable. He viewed time in much the same way.

It was not until the early 1900s when the mysteries of space and time, as well as the underlying causes of gravity, were addressed. Albert Einstein changed the course of history when he published his theories of special relativity (in 1905) and general relativity (in 1915). Einstein formulated that space and time are not absolutes, but have dynamic qualities associated with mass and motion. In fact, he described space and time as a unified whole, which later became known as space-time.

With special relativity, Einstein showed that measurements of time (and even distance) could differ for two observers, based on their relative motion. Time will elapse slower for someone in motion than it does for someone at rest. And the discrepancy in elapsed time will increase as the difference in the speed increases. In a sense, observers carry their own clock with them. This realization signifies another important point—that the observers would also disagree on what constitutes a given moment in time. One person’s now would be different from the other person’s now, yet both perspectives would be equally valid. Keep in mind, that it’s only when dealing with speeds approaching the speed of light or extreme distances that disagreements in time become significant. The effects of special relativity are not visibly apparent in the temperate conditions that exist here on earth; however, the earth is somewhat of an anomaly in comparison to the universe as a whole. With the universe, where extreme distances and speeds are commonplace, special relativity becomes important.

With general relativity, he showed that the effects of gravity are caused by the warping or curving of space (or space-time, but for simplicity I will use the term space). Heavy objects like planets and stars warp the fabric of space, thus creating the effects of gravity. It is similar to placing a heavy ball in the center of a trampoline. Any smaller balls placed on the surface will be drawn to the center, due to the surface being warped by the heavier ball. Bear in mind that a trampoline is a two dimensional representation of what is actually a three dimensional spatial fabric. It does, however, give us a clear visual analogy of how curved space participates in the motion of celestial bodies. In the case of planets and stars, orbits will develop when a stable balance is achieved. The earth can be thought of as moving in a straight line along a curved surface of space. Or as taking the path of least resistance along the distorted spatial fabric, which is created by the sun’s presence.

Another consequence of general relativity is that just as gravity curves space, it also curves time. But what does curved time mean? Similar to special relativity, where motion alters time, general relativity claims that gravity also alters time. When gravity exerts its influence time slows down. For instance, time passes a little slower on the surface of the earth than it does for objects high above the earth. A practical example of this effect is in the technology behind global positioning systems (GPS). The satellites that guide GPS devices have to account for both special and general relativity (general relativity producing the largest effect). The internal clocks of the satellites account for the fact that clocks on the earth’s surface run slower. If not for these adjustments, GPS devices would quickly become inaccurate; the coordinates on the ground would drift off by several kilometers each day.

Einstein’s relativity goes against our common sense perceptions, but apparently this is the reality of the universe. Einstein’s insights led to modern cosmology (the study of the origin and evolution of the universe), and our current view of the universe. Both classical physics (Newton’s view) and relativity (Einstein’s view) provide a deterministic framework. That is, if the present conditions are known, the past and future conditions can also be determined. That’s assuming that you have all the present data and the mathematical ability to do the calculations.

The next scientific breakthrough would be of a very different nature. In the mid-1930s a group of scientists were unlocking the secrets of the atom. In so doing, it led to the development of quantum mechanics. They found that the atomic and subatomic realms behave in ways that are very different from the world experienced at the larger scales. A whole new set of laws had to be developed to deal with the bizarre nature of the atom—laws that are partly governed by randomness and probabilities. Physicist Brian Greene describes the nature of quantum mechanics. He writes in The Fabric of the Cosmos:

“…according to the quantum laws, even if you make the most perfect measurements possible of how things are today, the best you can ever hope to do is predict the probability that things will be one way or another at some chosen time in the future, or that things were one way or another at some chosen time in the past.”

The probabilities that are used in quantum mechanics are more fundamental than the probabilities that are assigned to everyday events. When we assign a probability to a game of dice or blackjack, it is based on our inability to calculate the precise conditions that will determine the outcome of the event—specifically, each roll of the dice or flip of the card. With quantum mechanics, however, even if we know all the present information possible, we still can not predict a future outcome with absolute certainty. Quantum physics describes a reality that is fundamentally uncertain, in which objects have no definite position, take no definite path, and even have no definite past or future.

Some experiments (known as the double-slit experiment and variations of it) have actually shown that a single particle, such as a light photon, can behave as if it simultaneously takes a number of different paths from a source to a target. It is debatable whether this really happens; nonetheless, outcomes are determined by the number of possible paths of the photon, whether or not they are all realized. The photon takes a definite position only when it is observed or measured (when it strikes the target). In between the source and the target, it can be thought of existing as a haze of possibilities.

This is partially explained by the idea that subatomic objects, like photons and electrons, exhibit both wave-like and particle-like properties. At times, a photon or electron can be described as occupying a wide region in space, and at other times described as occupying a single point in space. Depending on the variation of the double-slit experiment, a photon can sometimes behave like a wave and sometimes behave like a particle. Although it is not entirely clear how these results should be interpreted, physicists agree that our conventional sense of reality does not apply at the quantum level—even to a larger degree than Einstein’s relativity.

I know this all sounds absurd. Nevertheless, the predictions of quantum mechanics have produced results that are extraordinarily accurate. Quantum mechanical predictions are accurate in the sense that if a sufficient number of identical experiments are carried out, the totality of the outcomes will reflect the assigned probabilities. Yet each single experiment will generate a random and unpredictable outcome. Therefore, even with the most precise calculations possible, there is an unavoidable degree of uncertainty in quantum mechanics.

It has been said that nobody understands quantum mechanics, that even scientists that work with quantum mechanics don’t understand it. So if it’s not sinking in, don’t lose any sleep over it. In summing up: the renowned physicist Richard Feynman once wrote in The Strange Theory of Light and Matter “[Quantum mechanics] describes nature as absurd from the point of view of common sense. And it fully agrees with experiment.”

Once again our common sense is challenged by the laws of physics. From classical physics to the updating of relativity, and the weirdness of quantum mechanics, reality is proving to be difficult to grasp, as these theories give us very different views of reality. For this reason, there is a consensus among some physicists that there exists a deeper level of reality to the universe that remains undiscovered. They propose that there should be one theoretical framework that describes the universe, and not a fragmented view based on several partial theories. Einstein called this hypothetical theory a unified theory (also called the theory of everything). The quest for a unified theory became one of Einstein’s passions during his later years; however, it was not realized during his lifetime.

Today, physicists are still seeking the elusive unified theory. Our present understanding of the universe is based on the two major breakthroughs of the 20th century. 1) General relativity, which describes the large scale structures of the universe, like stars and galaxies. 2) Quantum mechanics, which describes the small scale structures, like molecules and atoms. These two theories have been very successful in their own right, but in some extreme situations they cannot be applied successfully. In some situations where large densities are compressed into a tiny region of space, an understanding of both the large and the small is required. But when general relativity is applied together with quantum mechanics, the theories fall apart. This becomes a major obstacle when trying to understand conditions such as the center of black holes and the origin of the universe where these conditions need to be considered. The big bang theory describes the events a fraction of a second after the beginning, but says nothing about the beginning or before. Without a unified theory, or a new theory altogether that can deal with this situation the cause for the origin of the universe will remain a mystery.

As we have seen, each new discovery has added a piece to the puzzle and our understanding of the universe has increased dramatically over the years. The ultimate goal of science can be nothing other than a complete understanding of the laws of nature, though it may be that mystery will forever be a part of the picture. In his 1988 book, A Brief History of Time, Stephen Hawking weighs in on the subject:

“But can there really be such a unified theory? Or are we perhaps just chasing a mirage?

There seems to be three possibilities:

1) There really is a complete unified theory, which we will someday discover if we are smart enough.

2) There is no ultimate theory of the universe, just an infinite sequence of theories that describe the universe more and more accurately.

3) There is no theory of the universe; events cannot be predicted beyond a certain extent but occur in a random and arbitrary manner.”

There may very well be limits to what humans are able to understand, but this should not limit our quest for knowledge. Where would we be today if some people hadn’t questioned conventional thinking and opened the door to greater discovery? It is due to the few who dared to challenge the beliefs of their time that many benefited. Not only in science, but in other domains as well, it is the quest for knowledge that paves the way for progress. This is the case for our lives, as well as humanity as a whole. No one knows how far we can go, and only time will tell. On this note, we can at least rest assured that the modern age of science has brought humanity out of the darkness of ignorance, and into the light of knowledge.

On July 20, 1969, the first humans landed on the surface of the moon. This was an incredible achievement. The Apollo spacecrafts were guided by technology that had less computing power than a modern smartphone. The equations used to plot the course to the moon were devised by Isaac Newton in the 1600s. The lunar landing is a milestone that links the Scientific Revolution of the 15th and 16th hundreds and 20th century science. For science to have progressed this far, it had to be rescued from centuries of insignificance.

The Scientific Revolution refers to an era when mankind developed the methods that led to our modern scientific view. Ancient Greece started the scientific process, and then it stalled during the Middle Ages when human progress remained at a standstill. The Scientific Revolution occurred mainly in Europe, and it coincides with the Age of Enlightenment. This was an age of reason, when individuals searched for truth by their own means. The revolutionary scientists (natural philosophers) did not blindly accept old ideas; they came to their own conclusions.

Breaking the Spell of Tradition

For much of human history, tradition was the authority. The rules were set by the state or the religion of the time and they were strictly enforced. During the Middle Ages the Catholic Church was the unquestioned intellectual authority. Free expression of ideas was not tolerated and the main source of knowledge was church doctrine. This not only applied to spiritual matters, but also to nature and the universe.

Progress was not deemed to be possible by human methods. Only God had the power to intervene and change the direction of human life. The goal of the church was to maintain the ideals outlined in scripture, and not to question whether new ways could make life better. I suspect that a large portion of society had accepted their lot in life; however, some free thinkers questioned the authority of tradition. A new way of thinking about humankind’s ability and responsibility for directing life began. This was the impetus for the Scientific Revolution.

The Methods and Mathematics of Galileo and Newton

Galileo died in 1642, the same year that Newton was born. These two men were probably the most influential scientists of the Scientific Revolution. Both men have been called “the father of science.” This may be an oversimplification of history, as there was surely a movement, which many contributed to the scientific cause. Nevertheless, Galileo and Newton stand out with both their discoveries, and their methods.

If relying on old books and tradition was not sufficient, a new way was needed to understand the world. Galileo came before Newton: Galileo established observation and experiment as the pillars of science. In order to determine if something was true, it had to be tested. Even the senses were considered unreliable in some cases. He also used mathematics to calculate the motion of objects. The idea that nature could be described using numbers was revolutionary. The scientific method had taken root.

Galileo’s confrontation with the church is well-known and is an iconic turning point in history. For 1500 years the church supported an earth-centered model of the universe; it was considered heresy to challenge this view. In 1632, Galileo published his most famous work, Dialogue Concerning the Two Chief World Systems. He wrote a dialogue showing both sides (earth-centered model and sun-centered model) hoping it would avoid church censorship. However, it was clear that Galileo supported Copernicus’ model from an earlier publication in 1543. This model placed the sun stationary at the center, with the earth, planets and stars orbiting the sun. The church banded the book and sentenced Galileo to house arrest, where he spent the last decade of his life.

Galileo came to his conclusion because the evidence led him to do so. Truth was not a matter of faith, belief or tradition. Ultimately, objective evidence was the determining factor. Using a telescope, which he built, he observed 4 moons orbiting Jupiter. This was proof that not every celestial body circled the earth. He also observed the phases of Venus (similar to lunar phases). The phases were caused by Venus’ orbit around the sun inside the Earth’s orbit. He concluded that the Copernican Model of the universe was the correct model. Galileo was right, and the world eventually agreed with him.

If there was any doubt that science could explain the world, by the time Isaac Newton was done it had been dispelled. According to some present scientists, Newton was the most brilliant scientist that ever lived. In 1687, he published the Principia Mathematica, where he disclosed his law of universal gravitation and the three laws of motion. With Newton’s laws one could calculate the motion of objects in both the heavens and the earth, including the trajectory of a spaceship flying to the moon. For Newton, God’s hand was present in the laws of nature.

Although not as publicized, Newton also made influential discoveries in optics. He discovered that white light is a mixture of the different colors of the rainbow. White light can be spread out into a spectrum of colors. This phenomenon would prove to be critical in charting the universe a few centuries later. We now know a tremendous amount about the large-scale universe because scientists can decode light. Information can be extracted from the light of distant galaxies. This is done by studying the fine details of the spectrum.

Galileo, Newton and the revolutionary scientists showed that the book of nature was accessible to human understanding. And the avenue was the scientific method and mathematics. This was just the beginning, as Newton realized:

“I was like a boy playing on the sea-shore, and diverting myself now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.”

Transforming the World

The early scientists were like the pioneers that sailed to discover the New World. The explorers were trying to claim and settle new lands, but they could not predict the types of civilizations that would follow. Similarly, the initial goal of science was to understand how nature worked. The applied sciences would come later. Newton never imagined that his equations would be used to place a man on the moon. The physicists of the early 1900s that studied the atom did not foresee the internet and smartphones.

The first step was to discover the laws that governed the universe. Then gradually it became apparent that nature could be manipulated for man’s benefit. Science had a say in the philosophical questions by challenging long-held beliefs, but it also changed humanity’s way of life. In the last 500 years the world has seen more changes than any other time period. This is mainly due to the Scientific Revolution and the Industrial and Technological Revolutions that followed.